The following exception is thrown when "<withJansi>true</withJansi>" is used with  ConsoleAppender on Windows (full stack trace in attached log file):

16:39:40,801 |-WARN in ch.qos.logback.core.ConsoleAppender[STDOUT] - Failed to create WindowsAnsiOutputStream. Falling back on the default stream. ch.qos.logback.core.util.DynamicClassLoadingException: Failed to instantiate type org.fusesource.jansi.WindowsAnsiOutputStream
at ch.qos.logback.core.util.DynamicClassLoadingException: Failed to instantiate type org.fusesource.jansi.WindowsAnsiOutputStream
at at ch.qos.logback.core.util.OptionHelper.instantiateByClassNameAndParameter(OptionHelper.java:69)

...

Caused by: java.lang.ClassNotFoundException: org.fusesource.jansi.WindowsAnsiOutputStream cannot be found by ch.qos.logback.classic_1.2.3
at at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:432)
at at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:345)
at at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:337)
at at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:160)
at at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at at ch.qos.logback.core.util.OptionHelper.instantiateByClassNameAndParameter(OptionHelper.java:56)
at ... 49 common frames omitted

the jansi library correctly exports this package and logback-core correctly imports the same package.

It seems that the following entry is missing in logback-classic's MANIFEST.MF file:

org.fusesource.jansi; resolution:=optional; version="[1.9, 2)"